This invention relates to food products, especially refrigerated fermented dairy products such as yogurt that are calcium fortified and to their methods of manufacture, and more specifically to yogurt fortified with calcium.
The present invention provides improvements to those calcium fortified yogurt products and methods of preparation that are described in U.S. Pat. No. 5,820,903 entitled xe2x80x9cCalcium Fortified Yogurt and Methods of Preparationxe2x80x9d (issued Oct. 13, 1998 to Fluery et al.) and which is incorporated herein by reference. The ""903 patent describes the post fermentation addition of a calcium phosphate having a particle size of less than 150 microns to produce a calcium fortified stirred style yogurt. In important part, the present improvement resides in selecting and adding a more fine powder form of calcium phosphate having a particle size of less than six microns to a milk base prior to fermentation. By utilizing the more fine powder, it has been surprisingly found that pre-fermentation addition can be practiced. As a result, methods have now been found to produce either a stirred style yogurt product or a cup set fermented yogurt product from the same or similar calcium fortified milk base. Moreover, the process can be simplified relative to the post fermentation addition to eliminate the need for preparing a sterilized, pH adjusted calcium phosphate slurry for post fermentation addition.
Recent medical studies have indicated that a diet containing the U.S. recommended daily allowance (xe2x80x9cRDAxe2x80x9d) of calcium can be effective in preventing or mitigating osteoporosis, and also possibly high blood pressure and colon cancer. There is therefore great public interest in the consumption of food products that will supply the recommended daily allowance of calcium.
Nutritionists and consumers alike recognize dairy products as good sources of calcium. Consumers who may be most in need of an adequate calcium intake (e.g., dieters, the pregnant or middle aged women, and children) are target consumers for yogurt products.
An unfortified six ounce (170 g) serving of fruit-flavored low fat yogurt provides only approximately 200 to 250 mg of calcium (i.e., about 0.12% to about 0.15% calcium). The current RDA is 1000 mg. Thus, the natural calcium content of yogurt must be supplemented by fortification with added calcium in order for a single serving of yogurt to provide 100% or even 50% of the current RDA for calcium. This problem is even more severe for yogurt products containing up to about 20% fruit sauce since such fruit materials are low in native calcium content.
Serious practical difficulties have been encountered in incorporating supplemental calcium into dairy products because most calcium salts have very low solubility in milk. Indeed, in milk itself, up to 60 to 70% of the calcium exists as insoluble colloidal calcium phosphate associated with the casein micelles. Added calcium salts, being generally insoluble and not suspended by casein, therefore tend to settle out, frustrating attempts to maintain uniform dispersions during manufacture.
This problem of suspending insoluble calcium salts is compounded by the fact that generally the yogurt base should not be agitated during the incubation period, i.e., the yogurt should be quiescently fermented. Thus, in the manufacture of yogurt using vat incubation, the required lack of agitation during incubation can cause a substantial portion of an insoluble calcium salt to settle to the bottom of the vat. The salt then must be laboriously scraped off the bottom of the vat and blended into the yogurt. In light of these cleaning difficulties, this process is not only impractical using conventional yogurt manufacturing equipment, but also is likely to adversely affect the texture of the product. In the production of cup set or in cup fermented yogurt products, the fermentation step should also be quiescently fermented. Settling can result in a product unacceptable to the consumer.
The prior art, however, includes a variety of efforts to overcome the substantial problems of calcium fortification of yogurt. One approach to the calcium fortification of yogurt is disclosed in U.S. Pat. No. 5,449,523 (issued on Sep. 12, 1995 to Hansen) entitled xe2x80x9cProcess For The Manufacture Of A Calcium Fortified Yogurt With Improved Heat Stability.xe2x80x9d In this method, an expensive soluble source of calcium is employed. Adding to the cost of the ""523 patent is that the calcium content of the already expensive material is less than a third of the preferred salt, tricalcium phosphate, used herein. Moreover, the methods employed in the ""523 patent require the addition of chelating agents to avoid undesirable milk protein precipitation. Usage of such required chelating, however, can adversely affect the flavor of the product. The chelating source(s) contribute an undesirable flavor to the yogurt at the high levels necessary to fortify to 1000 mg calcium. More importantly, however, the cost of the calcium source is prohibitive for a commercially practical product.
Similarly, the art includes numerous teachings directed towards forming a highly soluble complex of citric acid, malic acid and calcium. (See, for example, U.S. Pat. No. 5,186,965 entitled xe2x80x9cCalcium Citrate Malate Compositionxe2x80x9d). While useful, such formulations require addition of expensive special ingredients or extensive processing to form the materials in situ.
Still another approach is to try to employ inexpensive insoluble calcium materials (see particularly, U.S. Pat. No. 4,784,871 entitled xe2x80x9cMethod For Producing Calcium Fortified Yogurt,xe2x80x9d issued Nov. 15, 1988 to Peter H. Park). The ""871 patent teaches admixing an acid soluble salt optionally with sugar with an essential acidic fruit blend. The acidic fruit blend is allowed to dissolve a portion of the calcium salt. About 5 to 45% of the product of the fortified fruit blend with the partially dissolved calcium is then admixed with a fermented yogurt base to prepare a calcium fortified fruit containing yogurt product. Sugar is added to the fruit to assist in the avoidance of lumping of the calcium phosphate salt. Thus, the invention relies upon the fruit to solvate a portion and to suspend the balance of the insoluble calcium within the yogurt product.
While useful, not all yogurt flavors popular today contain fruit. Thus, it would be desirable to be able to provide a calcium-fortified yogurt that did not require the presence of a fruit ingredient. Moreover, it would be desirable to provide a reduced calorie yogurt fortified with calcium that did not require sucrose. Thus, the present invention can be viewed as an improvement upon the product and methods of the ""871 patent.
Also, it is desirable to have methods of calcium fortification that can be practiced by yogurt producers that can be used to provide both stirred style as well as cup set style yogurts using, to the extent possible, common techniques and equipment.
In view of the state of the art, there is a continuing need for new and improved yogurt products, particularly those providing enhanced nutritional benefits.
Accordingly, it is an objective of the present invention to provide new nutritionally improved yogurt products and their methods of preparation. A further objective is to provide new and effective methods for calcium fortification of fermented dairy products such as yogurt.
Another objective is to provide methods for preparing calcium fortified yogurts that minimize milk protein precipitation.
Still another objective is to provide methods for calcium fortification that do not require usage of expensive calcium materials.
Another objective of the present invention is to provide new methods for preparing calcium supplemented yogurts fortified with inexpensive calcium materials.
Another objective is to provide improved calcium fortified yogurt products that exhibit both good taste and good texture.
Still another objective is to provide calcium fortified beverages, especially milk based beverages.
Still another objective is to provide calcium fortified milk whether refrigerated or ultra high treated milk.
Still another objective is to provide calcium fortified food products such as milk based beverages and milk based wet foods such as yogurt that are fortified with calcium from their native levels by addition of insoluble calcium.
Surprisingly, the above objectives can be obtained and improved calcium fortified yogurt products can be provided. The present invention resides, in part, in the discovery that by providing insoluble calcium salts, of a particular particle size, that improved organoleptically acceptable calcium fortified products can be obtained that do not require a fruit ingredient.
In its preferred process aspect, the present invention resides in methods of preparing a fermented dairy product fortified with calcium that is visually undetectable in the final product and of acceptable organoleptic attributes in terms of grittiness and chalkiness. The process involves the pre fermentation addition of calcium phosphate in the form of a fine powder essentially characterized by a mean diameter of xe2x89xa66xcexc. The methods comprise the steps of A) providing a warm pasteurized milk base having a native calcium content fortified with sufficient amounts of calcium phosphate of the requisite particle size to provide a total calcium content ranging from 110% to 500% of the native level and, B) inoculating the warm pasteurized calcium phosphate fortified heat treated milk base with a starter culture; and C) fermenting the inoculated milk base to provide a yogurt; and D) cooling the yogurt to arrest the fermentation to provide a chilled yogurt having a viscosity of at least 1500 centipoise (at 5xc2x0 C.). The fermentation step is preferably practiced in bulk fermentation tanks to provide stirred style yogurt products although in-cup fermentation can be just as easily practiced to provide set style yogurt products.
In one product aspect, the present invention resides in products prepared by practicing the present methods.
In another product aspect of one and the same invention, the present invention is directed towards high moisture food products fortified with fine calcium phosphate powder such as milk based foods or dairy products and especially fermented dairy products such as yogurt comprising a fermented dairy product base having a viscosity of at least 1500 cps (at 5xc2x0 C.) and a calcium phosphate salt in a quantity sufficient to bring increase the calcium content of the composition from about 250 to 1300 mg per 170 g serving (0.15% to 0.75% by weight, wet basis).
The calcium amounts include both the native level supplied by the milk source as well as the supplemental added calcium.
The calcium salt is selected from the group consisting of tricalcium phosphate, dicalcium phosphate, and their hydrates, and mixtures thereof.
The fine calcium phosphate powder comprises particles having a mean diameter 6 microns or less. (xe2x80x9cMean Diameter xe2x89xa66xcexcxe2x80x9d).